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US-12628586-B2 - Etching method including steps of an oxidation process, a gas based chemical process, and removal of chemical products

US12628586B2US 12628586 B2US12628586 B2US 12628586B2US-12628586-B2

Abstract

An etching method of etching Si or SiN existing on a substrate, includes: forming an oxide film on a surface of Si or SiN by performing a radical oxidation process on the substrate having Si or SiN; performing a gas-based chemical process on the oxide film; and removing reaction products produced by the gas-based chemical process, wherein the forming the oxide film, the performing the gas-based chemical process, and the removing the reaction products are repeated a plurality of times.

Inventors

  • Akitaka Shimizu
  • Masaki Hosono
  • Kaname Satou

Assignees

  • TOKYO ELECTRON LIMITED

Dates

Publication Date
20260512
Application Date
20211213
Priority Date
20201215

Claims (16)

  1. 1 . An etching method of etching Si or SiN existing on a substrate, comprising: forming an oxide film on a surface of the Si or the SiN by performing a radical oxidation process on the substrate in a process container; performing a gas-based chemical process on the oxide film; and removing reaction products produced by the gas-based chemical process, wherein the forming the oxide film, the performing the gas-based chemical process, and the removing the reaction products are repeated a plurality of times, wherein the radical oxidation process generates oxygen-containing plasma with an oxygen-containing gas and causes oxygen radicals in the oxygen-containing plasma to act on the surface of the Si or the SiN, wherein the oxygen-containing gas is a mixed gas including O 2 gas and a F-containing gas, wherein the substrate has a recess and the Si or the SiN is present on a side surface of the recess, and wherein the radical oxidation process includes controlling loading between a frontage and a deepest portion of the recess by adjusting at least one of a pressure in the process container and a ratio of the F-containing gas in the oxygen-containing gas.
  2. 2 . The etching method of claim 1 , wherein whenever the forming the oxide film is performed once, the performing the gas-based chemical process and the removing the reaction products are repeated a plurality of times.
  3. 3 . The etching method of claim 2 , wherein the forming the oxide film and the performing the gas-based chemical process are performed in a same process container.
  4. 4 . The etching method of claim 3 , wherein the removing the reaction products includes sublimating the reaction products from the substrate, and wherein the performing the gas-based chemical process and the removing the reaction products are performed in separate process containers.
  5. 5 . The etching method of claim 1 , wherein the oxygen-containing gas further includes at least one selected from the group of H 2 gas and a noble gas.
  6. 6 . The etching method of claim 5 , wherein the F-containing gas is a NF 3 gas.
  7. 7 . The etching method of claim 6 , wherein the oxygen-containing plasma is generated by remote plasma in a plasma generation space separate from a processing space in which the substrate is arranged, and the oxygen radicals in the oxygen-containing plasma are supplied to the substrate.
  8. 8 . The etching method of claim 7 , wherein the recess of the substrate has a depth of 4 μm or more.
  9. 9 . The etching method of claim 8 , wherein the gas-based chemical process is performed with a process gas including a fluorine-containing gas.
  10. 10 . The etching method of claim 9 , wherein the process gas including the fluorine-containing gas includes a fluorine-containing gas and a H 2 O gas or a reducing gas.
  11. 11 . The etching method of claim 10 , wherein the process gas including the fluorine-containing gas includes a HF gas as the fluorine-containing gas and includes an NH 3 gas as the reducing gas.
  12. 12 . The etching method of claim 11 , wherein the reaction products are an ammonium fluoride-based compound produced after the gas-based chemical process.
  13. 13 . The etching method of claim 1 , wherein the forming the oxide film and the performing the gas-based chemical process are performed in the same process container.
  14. 14 . The etching method of claim 1 , wherein the performing the gas-based chemical process and the removing the reaction products are performed in the same process container.
  15. 15 . The etching method of claim 1 , wherein the forming the oxide film, the performing the gas-based chemical process, and the removing the reaction products are performed in the same process container.
  16. 16 . The etching method of claim 1 , wherein the gas-based chemical process is performed with a process gas including a fluorine-containing gas.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from Japanese Patent Application Nos. 2020-207625 and 2021-159733, filed on Dec. 15, 2020, and Sep. 29, 2021, respectively, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to an etching method and an etching apparatus. BACKGROUND In the process of manufacturing a semiconductor device, there is a process of etching and slimming silicon (Si) or silicon nitride (SiN). Wet etching is often used in etching in such a process. For example, Patent Document 1 discloses a method of etching polysilicon by wet etching. PRIOR ART DOCUMENT Patent Document Patent Document 1: Japanese Laid-Open Patent Publication No. H09-260361 SUMMARY According to one embodiment of the present disclosure, there is provided an etching method of etching Si or SiN existing on a substrate, which includes: forming an oxide film on a surface of the Si or the SiN by performing a radical oxidation process on the substrate having the Si or the SiN; performing a gas-based chemical process on the oxide film; and removing reaction products produced by the gas-based chemical process, wherein the forming the oxide film, the performing the gas-based chemical process, and the removing the reaction products are repeated a plurality of times. BRIEF DESCRIPTION OF DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. FIG. 1 is a flowchart showing an example of an etching method according to an embodiment. FIG. 2 is a flowchart showing another example of the etching method according to the embodiment. FIG. 3 is a cross-sectional view showing an example of a structure of a substrate to which the etching method of the embodiment is applied. FIG. 4 is a view showing a state in which a poly-Si film serving as a channel in the structure of FIG. 3 is etched. FIG. 5 is a cross-sectional view showing another example of the structure of the substrate to which the etching method of the embodiment is applied. FIG. 6 is a cross-sectional view showing a state in which a SiN film of an ONON stacked structure portion is recess-etched, in the structure of FIG. 5. FIGS. 7A to 7C are diagrams showing a relationship between the number of cycles of Top, Mid, and Btm and an amount of Si etching when conditions of a radical oxidation step are changed in the structure of FIG. 3 to repeat the radical oxidation step and an oxide removal step. FIGS. 8A to 8D are views showing an estimation mechanism in which a top-bottom loading can be controlled by a pressure during a radical oxidation process and a ratio of a NF3 gas which is an F-containing gas. FIG. 9 is a partial cross-sectional plan view schematically showing an example of a processing system used in the etching method of the embodiment. FIG. 10 is a cross-sectional view schematically showing an example of a process module provided to the processing system of FIG. 9 and functioning as an etching apparatus for carrying out the etching method of the embodiment. DETAILED DESCRIPTION Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. <Etching Method> FIG. 1 is a flowchart showing an example of an etching method according to an embodiment. The etching method according to the present embodiment is to etch Si or SiN existing on a substrate. First, a substrate having Si or SiN, which is an etching target, is subjected to a radical oxidation process to form an oxide film on the surface of Si or SiN (in step ST1). Subsequently, the oxide film is chemically processed with a gas (in step ST2). Subsequently, reaction products produced by the chemical process in step ST2 are removed (in step ST3). These steps ST1 to ST3 are repeated a plurality of times. As a result, Si or SiN existing on the substrate is etched by a desired amount. Hereinafter, detailed description will be given. The radical oxidation process in step ST1 generates oxygen-containing plasma and causes oxygen radicals (O radicals) in the oxygen-containing plasma to act on the substrate accommodated in a process container to form the oxide film (SiO2 film) on the surface of Si or SiN. At this time, remote plasma may be used so that mainl